Drug & supplement interaction

Ephedra + Grepafloxacin

Grepafloxacin brand name: Raxar.

Major Interaction
Medically reviewed by · Updated September 2026
The bottom line Major

Grepafloxacin falls into 2 drug categories that Ephedra can interact with; the most serious is rated major. Theoretically, ephedra might have an additive effect with drugs that prolong the QT interval.

Read the full interaction report
SeverityMajor
LikelihoodProbable
Interactions2
EvidenceB
What do Severity, Likelihood & Evidence mean?
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Interaction report

Ephedra and Grepafloxacin

These two interact in 2 distinct ways. Each one is explained separately below.

Why Are There 2 Interactions?

Ephedra interacts with whole categories of medication. Grepafloxacin falls into 2 of those categories, so it can interact with Ephedra in 2 different ways. We’ve listed each one below — your overall risk is driven by the most serious of them (Major).

Major

QT INTERVAL-PROLONGING DRUGS

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Why this applies to Grepafloxacin

Grepafloxacin falls under QT INTERVAL-PROLONGING DRUGS — the group Ephedra interacts with.

Theoretically, ephedra might have an additive effect with drugs that prolong the QT interval.
Even in healthy volunteers, EKG changes including prolonged QT interval and premature atrial contractions have been reported with ingestion of recommended doses of ephedra. Ephedra may have an additive effect with drugs that prolong the QT interval. This may increase the risk of ventricular arrhythmias.
Severity Major Likelihood Probable Evidence B

Interaction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports..

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the key concern with this pairing. Grepafloxacin is a fluoroquinolone antibiotic that can stretch out the heart's electrical recovery time, something we call QT prolongation. Ephedra is a strong stimulant that, even at recommended doses, has caused EKG changes and an irregular heartbeat in healthy people. Put the two together and the effects can stack up.

The worry is a dangerous heart rhythm problem, with symptoms like a racing or pounding heartbeat, dizziness, or fainting. Honestly, ephedra is banned in U.S. supplements for good reason, so I wouldn't recommend it at all. If you've been taking anything containing ephedra (ma huang) while on this antibiotic, please loop in your pharmacist or doctor so they can guide you safely.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Jenkins DJ, Wesson V, Wolever TM, et al. Wholemeal versus wholegrain breads: proportion of whole or cracked grain and the glycaemic response. BMJ 1988;297:958-60. PubMed
  2. McBride BF, Karapanos AK, Krudysz A, et al. Electrocardiographic and hemodynamic effects of a multicomponent dietary supplement containing ephedra and caffeine: a randomized controlled trial. JAMA 2004;291:216-21. PubMed
  3. Gardner SF, Franks AM, Gurley BJ, et al. Effect of a multicomponent, ephedra-containing dietary supplement (Metabolife 356) on Holter monitoring and hemostatic parameters in healthy volunteers. Am J Cardiol 2003;91:1510-3, A9. PubMed
  4. Gardner, S. F., Franks, A. M., Gurley, B. J., Haller, C. A., Singh, B. K., and Mehta, J. L. Effect of a multicomponent, ephedra-containing dietary supplement (Metabolife 356) on Holter monitoring and hemostatic parameters in healthy volunteers. Am J Card PubMed
Moderate

CYTOCHROME P450 1A2 (CYP1A2) SUBSTRATES

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Grepafloxacin also falls under CYTOCHROME P450 1A2 (CYP1A2) SUBSTRATES.

Theoretically, ephedra might decrease levels of drugs metabolized by CYP1A2.
Some animal research suggests that ephedra induces CYP1A2 and increases the clearance of CYP1A2 substrates such as caffeine.
Severity Moderate Likelihood Possible Evidence D

Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the gist for grepafloxacin, an antibiotic in the fluoroquinolone family. Some animal studies hint that ephedra may speed up an enzyme called CYP1A2, which helps your body clear this drug. If that enzyme works faster, your grepafloxacin levels could drop a bit, and a lower level might mean it doesn't fight your infection as well.

I want to be honest with you: this is theoretical, based only on lab and animal data, so it's far from certain in real people. The bigger concern is ephedra itself, which is banned in U.S. supplements because it can dangerously raise blood pressure and stress the heart. Please don't combine these, and check with your pharmacist or doctor about safer choices.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Tang J, Zhou X, Ji H, Zhu D, Wu L. Effects of ephedra water decoction and cough tablets containing ephedra and liquorice on CYP1A2 and the pharmacokinetics of theophylline in rats. Phytother Res. 2012;26(3):470-4. PubMed

What These Ratings Mean

Every interaction above is graded three ways — here’s the key to each label.

Severity how clinically significant the interaction is
Major

Clinically significant. Avoid the combination, or use only under close professional supervision.

Moderate

Usually worth avoiding or managing — may need monitoring, a dose change, or timing apart.

Minor

Generally not serious. Be aware of it and mention it to your pharmacist.

Likelihood how strong the evidence is that the interaction actually happens in people
  • LikelyWell-controlled human studies have demonstrated the likely existence of this interaction.
  • ProbableInteraction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
  • PossibleInteraction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.
  • UnlikelyInteraction has been demonstrated in animal or in lab research but has been shown not to occur in humans.
Evidence the quality of the studies behind the rating (graded A–D)
  • AHigh-quality meta-analysis (quantitative systematic review).
  • BCase-control study.
  • CConsensus.
  • DAnecdotal evidence.

These ratings are for information only. Never start, stop, or otherwise change your therapy before speaking with your provider.

Keep it in perspective

Ephedra Also Interacts With Other Medications

Ephedra has 336 major, 496 moderate known drug interactions in our database — the Grepafloxacin one above is among them. If you take anything else, check it against the full list below.

Major 336 Moderate 496 No known interaction 1,998 (incl. Grepafloxacin)
Taking anything else?

Check Another of Your Medications Against Ephedra

Covers the 2,830 medications we’ve checked against Ephedra. Pick one to open its full report.

Everything else you take

See Every Supplement That Interacts With Grepafloxacin

This page covers Ephedra only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Grepafloxacin page lists 164 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), American Hellebore (major), Apple (major), Arsenic (major) and Cesium (major).

By severity: 9 major · 113 moderate · 42 minor.

From our pharmacist’s overview on the Grepafloxacin page

“A week on grepafloxacin (Raxar), a quinolone antibiotic, often comes with juice at breakfast, coffee through the day, maybe a probiotic for the stomach, and each of those shows up on this list. The nine major entries among these 164 deserve your attention first: grapefruit and other fruit juices can block the transporter that carries t…”

Reviewed by 2 · Jul 18, 2026

Open the Grepafloxacin interaction page

One more smart check

Taking Ephedra as Part of a Dietary Supplement Product? Check It for Interactions

We hold 37 real supplement products containing Ephedra, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Ephedra. Your product may carry other ingredients that interact with Grepafloxacin too, on top of Ephedra — and those would not show on this page. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Ephedra and Grepafloxacin Sit Against Everything Else

Out of every supplement and medication people look up on HelloPharmacist, here is where these two land this week — and which way each has been moving.

Supplement Ephedra
Top half

#583 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Grepafloxacin
Steady interest

#2,271 of 2,830 medications looked up here in the last 7 days

29 days ago today

Position among everything looked up on this site, not a measure of how commonly either one is used or how important it is. A supplement can climb this list because of a news story. It counts every request to the page, automated ones included, and nothing here identifies anyone.

Supplement

About Ephedra

What is Ephedra?

Ephedra
  • Weight loss
  • Nasal and sinus congestion
  • Asthma and breathing problems
  • Boosting energy and athletic performance
  • Allergies

Ephedra (ma huang) contains powerful stimulants like ephedrine that affect the heart and nervous system. Because it has been linked to serious harms including high blood pressure, stroke, and death, it is banned for use in dietary supplements in the U.S. and many other countries. We do not recommend using ephedra-containing supplements; talk to your pharmacist or doctor about safer, approved options.

Read the full Ephedra monograph & all interactions
Keep checking

Other Drugs & Ephedra

Browse every other medication we’ve checked against Ephedra — both the ones with a known interaction and the ones without. Select any drug for the full detail.

336Major
496Moderate
0Minor
1,997No known interaction
336 Major 496 Moderate 1,997 No interaction
Major

336 interactions

Showing 60 of 336 major interactions — see all 336 on the Ephedra page.

Moderate

496 interactions

Showing 60 of 496 moderate interactions — see all 496 on the Ephedra page.

No interaction 1,997 drugs checked — show the list

We also checked Ephedra against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 1,997 medications checked with no known interaction — see the full Ephedra list.

See the full Ephedra interactions page
See every supplement checked against Grepafloxacin, ranked by severity
Sources

Sources & How We Checked

Interaction details are evidence-graded and sourced from the Natural Medicines database. The medication overview comes from MedlinePlus.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

© 2021 Therapeutic Research Center, LLC

Keep exploring
Ephedra monograph › Uses, safety, and every drug interaction in one place Grepafloxacin supplement interactions › Every supplement checked against Grepafloxacin, ranked by severity Supplement interaction checker › Check any supplement or product against your medications Browse medications A–Z › Every drug we've checked against herbs & supplements Ask a pharmacist › Free, personal answer from our licensed team
Pharmacist Counseling Corner

Taking Ephedra and Grepafloxacin Together: Common Questions

Can you take Ephedra with Grepafloxacin?
This is rated a major interaction, so the combination is best avoided unless your doctor or pharmacist has specifically told you otherwise. Read the full details on this page and confirm with your pharmacist before combining them.
Why are there 2 interactions listed for Ephedra and Grepafloxacin?
Grepafloxacin belongs to more than one drug category, and Ephedra interacts with each of those categories a little differently. We list every one so nothing is missed — your overall risk is driven by the most serious of them.
How serious is the Ephedra and Grepafloxacin interaction?
We rate it Major. This is a clinically significant combination that is generally best avoided, or used only under the direct supervision of your physician or pharmacist.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

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This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.